I'm hoping someone can confirm what Buddhaghosa writes about in Path of Purification describing the centre of eye-consciousness being a little black speck the size of a pin head. The speck is in the centre of the eye. Has anyone read this? Confirmed this?

I'm a bit thrown off by your terminology. Well, if rupa is form and the eyebase is found in form, - yes. I believe the basis for the eye is the eyeball. And the basis for sight is external form. The condition for seeing is consciousness - or conscious contact between the basis for the eye and the external world. That would be my understanding. In regards to how one guards the senses, what is the proper method of approaching eye consciousness, given its proximity in the eye? Given the nature of its whereabouts in the eye? I would also have the same question for the other senses? Thank you.